The following is a tabulation of some prior art that presently appears relevant:
U.S. patentsPat. No.Kind CodeIssue DatePatenteeU.S. Pat. No. 7,416,108B2Aug. 26, 2008PhilipU.S. Pat. No. 5,127,969AJul. 7, 1992Sekhar
U.S. patent application PublicationsApplication NumberKind CodePublication DateApplicantUS 2009/0186238A1Jul. 23, 2009Clifford Bampton
Foreign Patent Application PublicationsApplication NumberKind CodePublication DateApplicantEP1759806A1Mar. 7, 2007Jungbluth et al.